Railway traffic controlling apparatus



01:1, 1,1949. R' M @ll-SDN F-'Hl- 2,216,614

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Aug. 22, 1939 INVENTORSPatented Oct. l, 1940 TRAFFIC CONTROLLING APPARATUS RAILWAY PATENroFrlCERobert M. Gilson and George W. Baughmain Pittsburgh, Pa., assignors toThe Union ASwitch & Signal Company, Swissvala Pa., a corporation .f

of Penns'ylvania u Application August 22, 1935:), ySerial No.r 291,386

1) Claims. (Cl. 246-34) ,Our invention relates to railway traflccontrolling apparatus and more particularly to apparatus for preventingfalse energization of the track relay due to foreigncurrent which may beinduced in the rails of the track from propulsion conductors or otherpower conductors carryingl heavy alternating current in proximity to therails of the track.

We shall describe twoforms of apparatus embodying our invention,v andshall then point out the novel features thereof in claims.

In the accompanying draviring, Fig. lis a diagrammatic View showingl oneform ofapparatus embodying our invention as applied to a simple `type ofnon-coded,` electric road track circuit. Fig. 2 is a diagrammatic Viewshowing a modified form of the apparatus of Fig. 1, also embodying ourinvention, as applied to a coded electric road trackcircuit adapted forcontrolling train movements in either direction. Y

Similar reference characters refer to similar parts in each of the twoviews.

In electrified territory where alternating current isused as thepropulsion energy, it is necessary for reasons of safety to Iemployalternating current of a different frequency forenergizing the trackcircuits which control the essential signalingapparatus on which safetyof train movement depends. The frequency separation betweenthetpropulsion and track circuit currents is ordinarily such as willinsure 'that the trackcircuit apparatus will not operate falsely at themaximum values of propulsion current tovWhich such apparatus may besubjected in service.v For example, Where the propulsion currentfrequency is 25 cycles, then 60 cycle orA 100 cycle signaling currentmay be used. Immunity is obtained by using a frequency selective trackrelay such, for example, as a centrifugal frequency relay or a vanefrequency relay. These relays are well known and it Will be sufficientto say that the centrifugal relay employs arotating, inertia element ofthe fly-ball governor type so designed as to be incapable of closingcertain contacts at the relatively low speed whichthe rotating elementattains when energized by current of the propulsion frequency. Y

If the'propulsion current which reaches the track relay is substantiallysinusoidal, no appreciable danger of false operation is present.Instances may occur, however, where thepropulsion current containsprominent harmonics and since the amount of track circuit currentnecessary for operating a track relay must necessarily be rather smallfor reasons` of sensitive track circuit from a source of alternatingcurrent of which shunting protection, Asuiiicient harmonic current mayat times be present to produce false operation of the track relay.Although it is the aim to cause the propulsion current to divide equallybetween the two rails of a track section in a multig5 ple track road,nevertheless, becauseA of unavoidable differenc'es in thebonding, selfand mutual inductance effects, and many other factors, a considerableunbalance in thepropulsion current asv betweenthe twofrails ofla trackcircuit is 1 0 frequently vmet with in practice. Moreover, in the eventof a broken rail and a trainoccupying the section, the'control elementof a track relay may acquire a substantial pro-pulsion potential whileat the same time, the local element may T15 also receive'an even `higherpropulsion potential from the signal transmission line upon which thetrack propulsion volte has Ybeen impressed in the step-updirection'through the track transformer. In this manner, false operationof the track relay may result. Also, a similar undesired effect may beproduced if sufficient induction in the vrails from power lines whichparallel the track section is present. For these reasons, some means notdependent on frequency separation alone` is essential "fo-r insuringsafety of track circuit operation on alternating current propulsionroads. Our inventiony enables this protection to .be obtained Ain asimple and reliable manner. 30 v Referring to Fig. '1, the referencecharacters I and la designate the ,track rails of a stretch ofalternating current propulsion railway which rails are divided byinsulated joints 2 to form a lacross the rails of the track, andalsohaving a local windin'g4. This local winding is energized only theterminals BX--CX are shown. 'I'he frequency of this source is, ofcourse, substantially different from that which supplies the propulsioncurrent. Both windings '3 and 4 must be simultaneously energized before.relay TR will pickup. v Located at thevother end ofthe section is atrackv transformer T having a primary winding 8'and av secondary Winding9. The latter winding furnishes operating 4current for the controlelement of 'relay TR through the current limiting device 55 R which maybe either a resistor or a reactor as determined by phase displacementconsiderations.

In order to prevent false energization of relay TR, we have provided atwo-element alternating current checking relay CR. As shown, one element5 of this checking relay is connected across the primary winding 8 oftransformer T, whereas the other element 6 of this relay is connected inseries with this same transformer winding. It will be apparent, however,from the description which follows that if desired, the element 5 may beconnected in multiple across winding 9 or across the terminals BX---CXvof the source, and that the element 6 may be connected in series withwinding 9 between the rails and the track transformer, with like effect.It is not necessary that the element 6 be included directly in theseries circuit with a winding of the tracktransformer as, obviously, asuitable transformer may be interposed in order to obtain the desiredoperating potential across the element 6. The relay CR, like the trackrelay, is so designed that it will pick up only when the two elements 5and 6 are simultaneously energized with current from the same source andonly if the proper relative instantaneous polarity exists between thesetwo elements. For maximum protection, relay CR may also be ofthefrequency selective type, such as the track relay TR. As long as relayCR remains energized and maintains its front contact 'l closedduringfthe time that the track section A-B is unoccupied, the trackrelay TR will remain picked up because its local winding 4 will receiveenergy over the front contact 'l and its control winding 3 will receiveenergy from the track in the usual manner. Should relay CR becomereleased for any reason, front contact 'l will open, thus causing relayTR immediately to release.

We shall now describe the way in which relay CR provides foreign currentprotection to the track relay. It will be noted that with thetransformer T properly energized from the source BX--CX through the fuseF and winding 6 of relay CR, then at a given instant, the instantaneousrelative polarity of the terminals of transformer winding 8 and of therelay winding 5 with respect to the other relay winding 6 will be asindicated on the drawing. Under this condition, pick-up torque will 'bedeveloped in the relay lCR. so that front contact 1 willbe maintainedclosed and will cause winding 4 of relay TR to be maintained energized.Also, the current supplied to winding 3 of the track relay TR over thetrack circuit will be of the proper polarity for developing normaltorque in this relay. Assuming, however, that an appreciable amount offoreign current is induced in the rails l and la from an adjacentpropulsion conductor or that unbalanced propulsion current containingprominent harmonies flows in the track transformer T, this current willcause winding 9 of the track transformer to act as a primary, inducingcurrent of the propulsion frequency in winding 8 of the transformer andstepping up the Voltage of this current due to the usual transformerratio. If we assume that at some given instant the instantaneouspolarity of Winding' 8 due to the foreign current induced therein isthat which is indicated on the drawing, then it will be readily apparentthat the instantaneous relative polarity of winding 6 due to the ow ofthe foreign current will become reversed from that which is shown onthedrawing. Therefore, although the instantaneous relative polarity ofwinding 5 of the relay CR due to the foreign current may be that shownon the drawing, the other winding E of this relay will have itsinstantaneous polarity reversed, so that the torque developed in relayCR due to the foreign current will be in the reverse direction and willcause front contact I to open and to release the track relay TR in theevent that the foreign current reaches a dangerous value.

A particularly dangerous condition which might arise on track circuitsin which protection such as herein disclosed is not provided, is thatoccasioned by broken wires or blown fuses at certain points in thesignaling current supply circuit such that the only load connected inmultiple with the input terminals of a given track transformer is thelocal element 4 of the track relay.- Under this condition, the voltageinduced in winding 8 by foreign current harmonics and stepped up throughthe track transformer would be particularly effective in aidingfalse'operation of the track relay because of the absence of additionalload which would ordinarily ltend to decrease the eifectivcnessof theforeign current. However, when a checking relay'such as CR is used, aheavy foreign current will cause a correspondingly strong rcversetorqueto be developed in this relay, thus reducing the possibility of falsepick-up of the track relay.:v

It will be apparent from the foregoing that the circuit connections ofthe checking relay are such that as long as the flow of track circuitlpower is in the direction from the -signaling source or transmissionline to' the-track,-' this relay will remain energized, butwhen thedirection ofthe ow of power is reversed,that is, when `foreign currentenergy is beingV fed from thetrack to the transmission line, therelativel instantaneous polarity 'of windings 5 and 6 with respect tosuch foreign current Will reverse, thus producing a vreverse torque inthe checking relay which will cause this relay tol release when theamount of the foreign current reaches adangerous value. It will beunderstood, of course, that the* development of a reverse torque in thechecking relayl in either direction. The track relay TRAis controlled asin Fig. l over a front contact l' ofthe checking relay CRA which causesthe local winding 4 to become deenergized whenever a dangerous amount offoreign current is present in the track transformer TA. The westboundtraic direction relay DRW controls the application of train control codeto the track circuit by means of transformer TB at location C forcontrolling westbound traffic. Similarly, the eastbound trafficdirection relay DRE controls the application of train control code tothe track circuit by means of the transformer TA at location D, thereby`controlling eastbound traflic. Relay DRE also at times controls'` overits front contact I2, the effective impedance of the transformer AT inthe track relay circuit for a purpose to be described hereinafter. Thecontrol circuits for relays DRW and DRE are well known and since thesecircuits -are unnecessary. for an understanding of our invention, adescription thereof Vwill not be given other than to state that wheneastbound traffic approaches-the section C-D from'the-left, relay DREwill be picked up and relay DRW will be released, whereas when Westboundtraffic approaches the section from the right, relay DRW Will be pickedup and'relay DRE will then be -released.

Relay AR is'an approach control relay which is effective Whenever thesection Cir-D becomes occupied, for starting the operation of the codetransmitter CT and for closing certain other circuits to be describedhereinafter. The checking relay CRA is a code following relay whichcon'- trois the local winding 4 cf relay TRA,"as before,

and which Ain addition, controlsthe impedance of the auxiliarytransformerV AT over its contact I3 in order to permit relay TRA toIpick up following the exit 0f a westbound train from the section.

Having described the' individual apparatus shown in Fig. 2, we shallnext describe the operation of this apparatus' when a train passes overthe section.

Normally, when no trainisin the section, the control element' 3 of thetrack rrelayis steadily energized from the rails by virtue of the factthat the track transformer TA is steadily' energized over a circuitwhich extends from one terminal BX of a suitable alternating currentsource, through front contact I-I' of the normally energized approachrelay AR, wire I E, front contact II-I8 of relay DRE (assuming that aroute has been established for eastbound traffic), wire i9, winding 6 ofrelay CRA, Wire 20, and winding u of track transformer' TA, to the otherterminal CX of the source. The impedance of Winding I0 of transformer ATwill be low because the other winding II of this transformer will beshortcircuited over the multiple connected' contacts i2, I3, and 23 ofrelays DRE, CRA, and AR, respectively. The local element 4`of relay TRAwill also be steadly energized over' a circuit which may be traced fromone yterminal BX, through front contact ill- I5 of relay AR, wires I6and 2 I, front contact l of relay CRA, wire 22, and winding A, to theother terminal CX of the source. Accordingly, relay TRA will vremainpicked up under this condition. Relay CRA will also be picked up becauseits element 6 will be steadily energized over the circuit previouslytraced for transformer TA, and its element 5 will'be steadily energizedover an obvious. circuit which includes front contact Iii-I5 of relayAR.v

When an eastbound train enters Athe section C-D, relay TRA will release,opening the circuit for the approach relay at front contact 2li. Therelease of relay AR will close back contact 25, starting the operationof the cozde transmitter CT, and will also establish a coding connectionfor wire I6 over back contact VI5--2Ii. It will be understood that thecode transmitter CT may be any suitable type of motor `operatedcontactor or reciprocating armature device which periodically andalternately closes the contacts 28-29 and 28-3I. Code will now besupplied to the track transformer TA and to the track rails ahead of thetrain over the same circuit previously traced fo-r transformer TA exceptnow extending from terminal BX, through the usual code selectioncircuits which are Well known rand are therefore not shown, forsimplicity, wire 21, contact 28--29 of the code transmitter CT, wire 3'0and back contact I5-26 of relay AR, to wire I6 and the remainder of thecircuit for transformer TA, previously traced. Relay CRA Ywill receivecode in both of its elements 5 and 6 over obvious circuits, and sincethis relay is designed to follow code, it will intermittently open andclose its contacts 'I and I3. No function is served by the periodicopening of these contacts under the eastbound trafo conditions exceptthat this operation provides a check on the mechanical integrity of thechecking relay.

When the train leaves the section, the removal of the train shunt Willcause coded energy to flow in winding 3 of the track relay, theimpedance o-f winding I0 being maintained at its low value due tothesteadily closed contact I2 of relay DRE and the periodically closedContact I3 of relay CRA. Coded energy will also simultaneously flow inwinding 4 of the track relay due to the periodic closing of contact 'Iso that relay TRA will pick up and in so doing will energize relay AR tode-` energize the code transmitter CT and to restore steady energy tothe apparatus over the front contact Ill-I5, thus restoring theapparatus to the condition in which it is shown in the drawing.

Assuming next that a westbound route has been established so that relayDRW is energized and relay DRE is deenergized, ifv a train` now enterslthe track section from the right, the track relay TRA will again becomedeenergized and will release relay AR. Relay AR will start the operationof the code transmitter, as before, but the energy received by the trackcircuit will under this condition be a combination of code supplied fromthe transformer TB for train control purposes and of steady energy fromthe transformer TA for the purpose of enabling the track relay to A*pick up after the train clears the section.

The circuit for energizing transformer TB may be traced from terminalBX,l through the code selection circuits, wire 2'I, contact 2li-3| ofcode transmitter CT, wire 32, front contact 33 of relay DRW, wire 35,back contact 35 of relay AR,

wire 36, and the input winding'of transforme-r TB, to the other terminalCX of the source. The

coded output from the transformer TB is impressed across the railsthrough a suitable current limiting reactor X. This coded output is noteffectively shunted by the track relay winding 3 lbecause of thesubstantial impedance simultaneously introduced by winding I0 at codeintervals when winding II is open circuited. The

latter winding will be on open circuit at code in- .a

tervals because contact I3 will open each time that contact 28-29 of thecode transmitter CT becomes open during the code cycle. Thus, the codefollowing operation of relay CRA provides a recurrent check showingwhether the train .j

has or has not left the section. `Element 6 of relayCRA will be'steadily energized over back contact Ila-31 of relay DRE, but sinceelement 5 will receive coded energy, relay CRA will follow code.

j vWhen the train leaves the section, the train shunt will be removedfrom relay TRA and this relaywil-l begin to receive pick-up energy assoon as a succeeding code impulse closes front contact i3 of relay CRAand causes the impedance of winding Iii` to drop toits low Value.Winding 4 will, of course, receive energy vsimultaneously `with winding3 so that relay TRA will pickup on to relay CRA over front contact ill-I5 so that this apparatus will again be restored to the condition inwhich it is illustrated.

If at any time when the section is either occupied or unoccupied, adangerous amount of propusion energy or other foreign current shouldappear in the winding 8 of the track transformer, the instantaneousrelative polarity of winding 6 due to such current will be immediatelyreversed with respect to winding 5 so that a reverse torque will bedevelopedin relay CRA which will cause this relay to become effectivelyreleased, thus eliminating the possibility of false operation of thetrack relay and the display of a less restrictive indication than thatwarranted by traffic conditions.

Although we have herein shown and described only two forms of railwaytraffic controlling apparatus embodying our invention, it is understoodthat various changes and modifications may be made therein within the-scope of the appended claims without departing from the spirit andscope of our invention.

Having thus'described our invention, what we claim is:

l. In combination with a section of railway track, a two-elementalternating current track relay having one element connected so as toreceive energy from the rails of said section, a source of alternatingcurrent, a track transformer having its input winding energized fromsaid source and having its output winding supplying energy to said oneelement of the track relay over the rails of said section, a two-elementalterhating current checking relay having one element energized fromsaid source and having the other element energized from a seriesconnection between said source and said transformer input winding, andmeans governed by said checking relay for controlling the energizationof the other element of said track relay from said source to therebymaintain said track relay normally energized, whereby in the event ofsufi'icient foreign current energy passing from said output to saidinput winding of the track transformer, the torque in said checkingrelay will reverse to cause said checking relay to release and so tocause 'said track relay to assume its deenergized position.

2. In combination with a section of railway track, a source of periodiccurrent, a track transformer having its input winding energized fromsaid source and supplying energy from its output Winding to the rails ofsaid section, a two-element track relay having one element connected soas to receive energy from said source over the rails of said section, atwo-element checking relay having one element energized from across awinding of said track transformer and having the other element energizedfrom a series connection With a winding of said track transformer, andmeans governed by said checking relay for controlling the supply ofcurrent from said source to the other element of said track relay.

3. In combination with a section of railway track, a source of periodiccurrent, a track transformer having its input winding connected withsaid source and having its output Winding connected across the rails ofsaid section, a tWoelement track relay having one element connectedacross the rails of said track, a two-element checking relay having oneelement connected across a winding of said track transformer and havingthe other element energized over a series `connection with a winding ofsaid track transformer, and means including a vcontact of said checkingrelay for controlling the supply of current from said source to theother element of said track relay.

4. In combination with a section of railway track, a source of periodiccurrent, a track transformer having its input winding connected withsaid source and having its output winding connected across the rails ofsaid section, a twoelement track relay having one element connectedacross the rails of said track, a two-element checking relay having oneelement energized from said source and having the other element includedin series beween said source and a winding of said track transformer,and means governed by said checking relay for controlling the supply ofcurrent from said source to the other element of said track relay tothereby maintain said track relay normally energized, whereby foreigncurrent energy flowing from the rails into said track transformer causesthe instantaneous relative polarity of one element of said checkingrelay to reverse, thereby causing the control function of said checkingrelay to become exercised if a dangerous amount of said foreign currentflows in said track transformer.

5. In combination with a section of railway track, a source of periodiccurrent, a track transformer having its input winding connected withsaid source and having its output winding connected across the rails ofsaid section, a twoelement track relay having one element connectedacross the rails of said track, a two-element checking relay having oneelement energized from said source and having the other element includedin series with a winding of said track transformer, and means includinga contact of said checking relay for controlling the supply of currentfrom said source to the other element of said track relay to therebymaintain said track relay normally energized, whereby foreign currentenergy owing from the rails into said track transformer causes theinstantaneous relative polarity of one element of said checking relay toreverse, thereby causing the control function of said checking relay tobecome exercised if a dangerous amount of said foreign current flows insaid track transformer.

v6. In combination with a section of railway track, a source of periodiccurrent, a track transformer having its input winding connected withsaid source and having its output winding connected across the rails ofsaid section, a two-element track relay having one element connectedacross the rails of said track, a two-element checking relay having oneelement energized from said source over a multiple connection with awinding of said track transformer and having the other element energizedfrom said source over a series connection with a winding of said tracktransformer, and means governed by said checking relay forcontrollingthe supply of current from said source to the other element of saidtrack relay to thereby maintain said track relay normally energized,whereby if a dangerous amount of foreign current energy flows from therails into said track transformer, said checking relay will opera-te tocause said track relay to release. f

7. In combination with a section of railway track, a source of periodiccurrent, a track transformer having its input Winding connected withsaid source and having its output winding connected across the rails ofsaid section, a twoelement track relay having one element connectedacross the rails of said section, a normally ineffective impedanceincluded in the connection of said one element with one of said rails, atwoelement checking relay having one element energized from said sourceover a multiple connection with a winding of said track transformer andhaving Ithe other element energized from said source over a seriesconnection with a winding of said track transformer, means governed bysaid checking relay for controlling the supply of current from saidsource to the other element of said track relay, and other meansgoverned by sa-id checking relay effective when said section is occupiedby a train entering from a given direction for rendering said impedancepeiodically ineffective to thereby enable said track relay to becomeenergized after said train leaves the section, whereby if a dangerousamount of foreign current energy flows from the rails into said tracktransformer, said checking relay will operate to deprive said otherelement of the track relay of energy, thereby insuring a release of saidtrack relay.

8. In combination with a section of railway track over which traiiic maymove in either direction, a source of periodic current, a tracktransformer having its input winding connected with said source andhaving its output winding connected across the rails at one end of saidsection, a two-element track relay energized from said source and havingone element connected across the rails at the other end of said sectionin series with an impedance, a traffic direction relay for eachdirection of traflc over said section, a two-element code followingchecking relay having one element energized from said source over amultiple connection with a winding of said track transformer and havingthe other element -energized from said source over a series connectionwith a winding of said track transformer, means including a frontcontact of one of said traffic direction relays in multiple y with afront contact of said checking relay for rendering said impedanceineffective, a front contact of said one traffic direction relayincluded in the energizing circuit for said other element of thechecking relay, said last named contactbeing included in the connectionof said track transformer with said source, means including a frontcontact of said checking relay for supplying current from said source tothe other element of said track relay, means including a back contact ofsaid one traffic direction relay for supplying current from said sourceto said track transformer 'and said other element of the checking relay,means including a front contact of the other of said traffic directionrelays effective when said section is occupied for supplying coded traincontrol current across the rails 'at said other end of the section, andmeans also effective when said section is occupied for supplying codedcurrent from said source alternately with said coded train controlcurrent to said one element of said checking relay to thereby cause saidchecking relay to follow code, whereby said impedance will be renderedineffective at code intervals to enable said track relay to pick upfollowing the eXit of a train from said section.

9. In combination with a section of railway track over which traffic maymove in either direction, a source of periodic current, a tracktransformer energized from said source and having its output windingconnected across the rails at one end of said section, a two-elementtrack relay having one element connected across the rails at the otherend of said section, a twoelement code following checking relay, atraffic direction relay, a code transmitter, means effective when saidsection is unoccupied forsupplying uncoded current from said source toone element of said checking relay, means effective when said section isunoccupied and said traffic direction relay is either energized ordeenergized for supplying uncoded current from said source to the otherelement of said checking relay and to said track transformer in series,means effective when said section is occupied and said traffic directionrelay is energized .for supplying coded current to both elements of saidchecking relay yand to said track transformer whereby said checkingrelay will follow code, means controlled by a front contact of saidchecking relay for energizing the other element of said track relay atcode intervals whereby said track relay will pick up when the sectionbecomes unoccupied, and means eifective when said track relay picks upfor discontinuing the operation of said code transmitter.

10. In combination with a section of railway track over which trafficmay move in either direction, a source of periodic current, a tracktransformer energized from said source `and having its output windingconnected across the rails at one end of said section, a two-elementtrack relay having one element connected across the rails at the otherend of said section in series with an impedance, a two-element codefollowing checking relay, a traffic direction relay, a code transmitterhaving a normal and a reverse contact, means effective when said sectionis unoccupied for supplying uncoded current from said source to oneelement of said checking relay as Well as to the other element of saidchecking `relay and said track transformer in series, means effectivewhen said section is occupied for initiating operation of said codetransmitter, means effective when said section is occupied and saidtrafc direction relay is energized for supplying train control code tothe rails at said other end of the section over said reverse contact ofthe code transmitter, means effective when said section is occupied forsupplying coded current to said one element of the checking relay oversaid normal contact of the code transmitter whereby said checking relaywill follow code, means controlled by a front contact of said checkingrelay for rendering said impedance ineffective at code intervals, meansalso controlled by a front contact of said checking relay for energizingthe other element of said track relay at code intervals whereby saidtrack relay will pick up when the section becomes unoccupied, and meanseffective when .said track relay picksy up. for discontinuing theoperation of said code transmitter.

ROBERT M. GILsoN. GEORGE W. BAUGHMAN.

